Twist drill grinding machines



June 11, 1957 K. E. R. ROSENBLOM 2,795,085

TWIST DRILL GRINDING MACHINES Filed June 8, 1951 4 Sheets-Sheet 1 June 11, 1957 K. E. R. ROSENBLOM 2,795,085

TWIST DRILL GRINDING MACHINES Filed June 8, 1951 4 Sheets-Sheet 2 June 11, 1957 K. E. R. ROSENBLOM 2,795,035

TWIST DRILL GRINDING MACHINES 4 Sheets-Sheet 3 Filed June 8, 1951 June 11, 1957 K. E. R. ROSENBLOM 2,795,085

v TWIST DRILL GRINDING MACHINES Filed June 8, 1951 4 Sheets-Sheet 4 United States Patent: 9

TWIST DRILL GRINDING MACHINES 'Karl Emil Rickard Rosenblom, Stockholm, Sweden Application June 8, 1951, Serial No. 230,460

Claims priority, application Sweden March 3, 1951 10 Claims. (Cl. 51-33) The present invention refers to a machine for the grinding of twist drills having two principal cutting edges located one on each side of the drill point.

The grinding machine according to the invention is substantially distinguished by the feature that the same comprises two cradles adapted to be oscillated about parallel axes lying in the same plane. The axis of each cradle is located between the other cradle and the axis thereof. One cradle carries a grinding disk adapted to be fed at right angles to the axes of oscillation and to be driven by a power motor. The other cradle carries a gripping holder for the fastening of the drill in grinding position for the two cutting edges thereof. Furthermore, the axis of the grinding disk and the centerline of the fastened drill are in their middle positions of the oscillatory movement located in the same plane extending through the axes of oscillation, either one of the cutting edges of the drill and the grinding surface of the grinding disk lying substantially alongside of each other immediately adjacent to the axis of oscillation of the cradle of the gripping holder.

The oscillatory movement of the cradle of the grind ing disk is adapted to be effected by means of a crank contrivance or the like, while the cradle of the gripping holder receives its oscillatory movement from a rotary cam disk synchronized with said crank contrivance. Furthermore, the gripping holder is swingably arranged about an axis coinciding with the middle plane of the grinding disk and intersecting the centerline of the drill and the axis of oscillation of the cradle of the gripping holder at right angles thereto. This cradle is swingable from a limit angular position on one side of the perpendicular to the last-mentioned axis of oscillation, which position constitutes the grinding position of one cutting edge of the drill, into a symmetrically located limit angular position on the other side of said perpendicular, which position constitutes the grinding position of the other cutting edge.

The above-described means of the grin-ding machine make it possible that the one and the other cutting edge may, through the synchronized oscillatory movements of the cradles, be alternately and successively ground by an intermittent feeding of the grinding disk toward the cutting edges of the drill, whereby the drill will be exactly centered and present cutting edges of the same length with correct clearance and cutting angles.

To further elucidate the principle of the invention, a suitable example of an embodiment of the grinding machine according to the invention will be described more closely in the following, further features characteristic of the invention being then also touched upon.

The description refers to the four annexed drawings comprising seven figures. Fig. 1 is a perspective view of the grinding machine regarded obliquely from the front, and Fig. 2 shows the right end wall of the same machine in elevation. Fig. 3 shows a vertical cross section on line llllll in Fig. 4 of the same machine. Fig. 4 shows a plan view of the same machine with the cradle of the grinding disk and numerous small details removed. Fig. 5 is a view in elevation and diagrammatically illustrates the oscillatory movements of the twist drill andthe grinding disk. Fig. 6 is a plan view and diagrammatically illustrates the reversal of the twist. drill from one grinding position to the other. Fig. 7 is an endwise view of thetwo principal cutting edges of a twist drill connected with the crosswise cutting edge thereof.

The twist drill grinding machine shown in Figs. l-4 is intended for manual operation and provided with a cast iron frame I placed on a box-like steel plate foundation 2. Secured to the upper border of the end walls of the frame are two pairs of horizontal pins, whichare coaxial and parallel in pairs. The ends of two arms 4 are mounted on the front pins 3 on the outside of the end walls, said arms carrying between them a grinding disk cradle 5, on the lower side of which is arranged a slide 6 displaceable in the transverse direction and carrying on the lower side thereof an electric motor 7, the shaft of which has a grinding disk 8 secured thereon, said grinding disk being partly enclosed within a casing 9,. The grinding disk cradle 5 is brought into an oscillatory movement, the middle position of which coincides with a horizontal plane, said movement being effected by means of a vertical rod 10, the upper end of which is pivoted to the one arm 4, while the lower end thereofis pivoted to one end of a lever 11 parallelling the arm 4 and having the opposite end thereof pivoted to a pin 12 on the right end wall of the frame 1. By this arrangement the rod will maintain its vertical position during the oscillatory movement of the grinding disk cradle 5. Secured to the middle portion of the rod 10 is a horizontal straight edge 13 having a roller 14 bearing against the lower side thereof, said roller being mounted on a crank pin 15. This crank pin extends horizontally from a slide 16, which is adjustable by means of a screw 17 in a radial slot hole 18 in a crank arm 19 on a horizontal shaft 20, which is rotated manually by means of a hand wheel 21 through a shaft 22 and a worm gearing 23. The upward movement of the oscillatory motion of the grinding disk cradle 5 is effected by means of the crank contrivance, while the downward movement of said cradle is efiected through its own weight. The grinding disk may be fed by means of a hand-wheel 24 adapted to displace the slide 6 in the transverse direction by means of a screw 24'. The angle of oscillation of the grinding disk cradle 5 may be varied by means of the screw 17.

Mounted on the two rear pins 25 inside the end walls are the ends of arms 26 carrying between them a horizontal cradle 27. From the middle portion on the lower side thereof extends downwardly and rearwardly an arm 28 Fig. 4, the lower end of said arm forming a sleeve 29,, in which is secured a pin 30, the center line of which extends through the common axis of the pins 25. Mounted on the pin 30 is a bushing 31, which carries a plane plate 32. at the top, the lower side of said plate following a plane surface on the upper side of a steel bar 33 bent on the line of a circular arc with the center thereof located on the center line of the pin 30. The bar 33 is secured to the plane upper side of the cradle 27. Mounted on the upper side of the plate 32 is a frame 34, on one side of which are arranged two jaws 35, 36 displaceable toward one another and adapted to be operated by means of a screw 37 provided with a right-handed thread portion and a lefthanded thread portion, said thread portions having different pitches. The screw 37 is rotated by means of a crank 38. The lower jaw 36 carries a displaceable and exchangeable angle-iron 39, the channel of which is adaptedto receive the twist drill 40 to be ground, with the point of the drill directed toward the grinding surface of the grinding disk. The gripping holder or vise formed by the two jaws 35, 36 is self-centering through certain means which do not form any part of the present invention as far as its features sought to be patented are concerned, so that when line fixedly connected with the cradle and intersecting the axis ,of the pin.30 while lying in a plane paralleling the bar33 and extending through the axis of oscillation 25 of thecradle 27. ,To fasten the drillin its proper axial position relatively to, the grinding disk with its two principal cutting edges in the proper angular position for grinding, the frame 34 is provided with anadiustingmeans 41 carrying a stop surface 42 and a mirror 43 (see Fig. 4). The adjusting means 41 may be tipped over by means of a hand-wheel 44, so that the stop surface 42 will intersect the extension of the center line of the drill 40. In effecting the adjustment the drill is advanced in the channel 39, until its point strikes against the stop surface 42, whereupon the drill, one cutting edge of which is reflected in the mirror, 43, is turned until said cutting edge coincides with a trace on the mirror, after which the channel 39 with the drill therein is advanced into grinding position and fastened by means of the crank 38. The drill is now in the proper position relatively to the grinding disk 8 for the grinding ofthe two principal cutting edges.

The vise 35-38 is swingable around the pin 30 by means of a handle-45 from a limit angular position on the righthand side, in which position the right-hand, downwardly directed cutting edge is to be ground, into a limit angular position on the left-hand side, in which grinding position the left-hand, upwardly directed cutting edge is to be ground. The swinging angle of the vise must be equal to the supplement-angle of the point angle of the drill to be ground. The drill 40-shown in Fig. 4 has a point'angle of 120. The swinging angle then becomes 60, that is to say equalling an angle of 30 on both sides of the middle position, which is indicated by a line 46 extending at right angles to the axis of oscillation of the cradle 27 and intersecting the axis of the pin 30. The swinging angle of the vise consequently must permit of being varied to adapt the grinding machine to twist drills with different point angles. To this end the circularly curved bar 33 is provided at both ends thereof with a row of radially cut notches 47 adapted tobe engaged by a pawl 47 on the. vise to retain the latter in the proper grinding position.

The oscillatory movement of the vise cradle 27, the middle position of which is a horizontal plane coinciding with the middle position the cradle of the grinding disk, is adapted tobe effected by means of a cam disk 48 arranged on the shaft 20, whereby the movements of both cradles become synchronized. The edge of the cam disk 48 bears on-a roller 49, which is mounted in the eccentrically arranged bifurcated end portion 50 of a shaft 51. which is mounted transversely in the cradle 27 and may be turned a half revolution by means of a hand-wheel 52, the roller 49 being then tipped over to bear on the edge of another cam disk 53, which is arranged on the .same shaft 20 and the curvature of which is of a different con: figuration. The upward movement of the oscillatory motion of thevise cradle 27 is effected by the one cam disk, while its downward movement takes place through the own weight of the cradle.

The synchronized oscillatory movements of the cradles 5 and27 appear from Fig. 3. Here, the grinding disk cradle 5 is performing its downward movement toward the horizontal middle. position 54. The angular movement is indicated by the arrow 55. In its downward movement the cradle 27 has reached the horizontal middle position 54 at the same time. The movement is indicated by the arrow 56. In the position shown, a grinding operation has just been terminated on the right-hand, downwardly directed cutting edge. At this time the vise is to be reversed into the left-hand grinding position by means of the handle 45 to impart a grinding,v operation to the left-hand, outwardly directed cutting edge by the grinding disk, which latter is swung downwardly thereat and then upwardly. Before its upward movement has reached the middle position 54, the vise is reversed back into the right-hand grinding position. The time of reversal is indicated by an audible or visible signal 20' operated by means of the rotary movement of the shaft 20 or by the movement of the vise cradle 27.

In the grinding operation the grinding disk 8 is advanced manually bymeansof the hand-wheel 24 toward the cutting edges by 0.05 to 0.15 mm. immediately before each other reversal of the vise. During the grinding operation it will be found suitable by means of a nozzle 57 to spray a cooling agent from a pump over the point of the drill. In using the method indicated above for the grinding of twist drills, the above-described machine is capable of grinding drills varying in diameter between .5 and 50 millimeters. By this grinding the principal cutting cdges will be exactly of the same length with accu rate centering and with accurately correct clearance and cutting angles. Reversal of the grinding machine for different drill diameters and clearance angles is effected by an alteration of the oscillatory angle of the cradle of the grinding disk by shifting the crank movement thereof by means of the screw 17. Obviously, the machine may be provided with a plurality of cam disks, the roller 49 being then adapted to bear on any one of them.

Fig. 5 is a diagrammatic illustration of the motion of the drill 40 and the grinding disk 8 in the vertical dircction. Fig. 6 is a diagrammatic illustration of the reversal of the drill 40 from one grinding position to the other. Fig. 7 is an endwise view of the drill 40 with the principal cutting edges 58 taking the correct angular position for grinding.

The grinding machine above described and shown in the drawings is intended for manual operation, the reversal of the vise and the advancement of the grinding disk being also effected manually. However, the machine can obviously be made to operate semi-automatically or automatically. In a semi-automatic grinding machine according to the invention, the movements of the cradles are effected by means of a separate motor, while the reversal of the vise and the advancement of the grinding disk are effected manually. In an automatic grinding machine, the reversal of the vise as well as the advancement of the grinding disk are effected by means of servo-motors, which are synchronized with the move ments of the cradles, and which are preferably operated by pressure impulses of a compressed fluid from a synchronized distributing arrangement.

In the manual operation of the machine the work piece to be ground is secured upon one of the cradles in the exact position desired and the grinding wheel 8 is fed to the proper position. The two cradles 5 and 27 are then caused to perform synchronous swinging movements in opposite directions so that the two portions of the drill to be ground pass successively into engagement with the grinding wheels.

It is obviously possible to modify the construction of the grinding machine in many ways without departing from the principle of the invention.

Having now described my invention, what I claim as new and desire to secure by Letters Patent is:

1. Machine for the grinding of twist drills having two principal cutting edges each located on one side of the drill point, comprising two cradles, means for mounting said cradles to oscillate about parallel axes of oscillation, the axis of oscillation of each cradle being located between the other cradle and the axis of oscillation of said other cradle, respectively, and one of the cradles carrying a grinding disk, a motor connected for driving said grinding disk, means for mounting said motor so as to be advanced at right angles to the axes of oscillation, said other cradle carrying a gripping holder for fastening said drill in grinding position, means for securing said gripping holder,v to said other cradle, the axis of the grhiding disk and the center line of the fastened drill lying in the middle positions of their oscillatory movements in the plane through the axes of oscillation, either one of the cuting edges of the drill and the grinding surface of the grinding disk lying substantially alongside of each other immediately adjacent to the axis of oscillation of the cradle of the gripping holder, a crank connected with the grinding disk cradle for imparting oscillatory movement thereto, while the cradle of the gripping holder receives its movement from a rotary cam disk, drivingly connected with the cradle of the gripping holder, means for synchronizing the rotary movement of said cam with the movement of said crank, means for swingably mounting said gripping holder to swing about an axis lying in the middle plane of the grinding disk and intersecting the center line of the drill and the axis of oscillation of the latter cradle at right angles thereto from a limiting angular position one side of the perpendicular to the lastmentioned "axis of oscillation, which position constitutes the grinding position of one cuting edge of the drill, to a symmetrically located limiting angular position on the other side of said perpendicular, which position constitutes the grinding position of the other cutting edge, said arrangements making it possible that one or the other cutting edge may, through the synchronized oscillatory movements of the cradles, be ground alternately and successively by an intermittent advancement of the grinding disk toward the cutting edges of the drill, whereby the drill will be exactly centered with cutting edges of the same length.

2. A grinding machine for twist drills according to claim 1, and in which the swinging angle of the gripping holder between the two grinding positions of the cutting edges is variable at will to adapt the grinding machines to twist drills with different point angles.

3. A grinding machine for twist drills according to claim 1 and in which the angle of oscillation of the cradle of the grinding disk is variable by means of a crank shaft having an adjustable length of stroke to adapt the grinding machine to twist drills with different diameters and to vary the clearance angle and the cutting angle of the cutting edge in grinding.

4. A grinding machine for twist drills according to claim 1, and in which the oscillatory movement of the cradle of the gripping holder is variable at will by the cam disk being replaced by a cam disk of a different configuration to cooperate synchronously with the cradle of the grinding disk in the grinding of twist drills with different diameters and with different clearance and cutting angles for the outing edges of the twist drills.

5. A grinding machine according to claim 1, and in which the means to impart an oscillatory motion to the cradle of the grinding disk comprises a crank with an adjustable length of stroke which is arranged on the same driving shaft as the cam disk device for the oscillatory motion of the cradle of the gripping tool.

6. A grinding machine according to claim 1 and in which the gripping holder is constituted by a vise with two clamping jaws.

7. A grinding machine according to claim 1, and in which the gripping holder is provided with an adjusting means for accurate adjustment of the point of the drill in an axial direction relatively to the grinding surface of the grinding disk, said adjusting means being provided with a stop surface adapted to be positioned by means of a hand-wheel so that said stop surface intersects the extension of the center line of the drill, the point of which may then be moved against the stop surface to cause the drill to take an exact axial position.

8. A grinding machine according to claim 1, and a manually operable feed screw for advancing the grinding disk toward the cutting edges of the drill.

9. A grinding machine according to claim 1, and in which a manually operable hand wheel is provided for effecting the oscillatory movements of the two cradles through a worm gearing connected therebetween.

10. A grinding machine according to claim 1, and in which the gripping holder is provided with an adjusting means for accurate adjustment of the point of the drill in an axial direction relatively to the grinding surface of the grinding disk, said adjusting means being provided with a stop surface adapted to be positioned by means of a hand-wheel so that said stop surface intersects the extension of the center line of the drill, the point of which may then be moved against the stop surface to cause the drill to take an exact axial position, said adjusting means being provided with a mirror surface adjacent to said stop surface, said mirror surface rendering an image of one cutting edge of the drill in the exact axial position thereof, so that the cutting edges of the drill may be adjusted into correct angular positions for grinding by turning the drill.

References Cited in the file of this patent UNITED STATES PATENTS 288,069 Landers Nov. 6, 1883 292,229 Johnson Jan. 22, 1884 327,758 Birkenhead Oct. 6, 1885 337,549 Bancroft Mar. 9, 1886 1,052,073 Mallory Feb. 4, 1913 2,098,267 Weishampel Nov. 9, 1937 2,252,303 Oliver Aug. 12, 1941 2,580,884 Bowman Jan. 1, 1952, 

